Radio access networks (RANs) provide for radio communication links to be arranged within the network between a plurality of user terminals. Such user terminals may be mobile and may be known as ‘mobile stations’ or ‘subscriber devices.’ At least one other terminal, e.g. used in conjunction with subscriber devices, may be a fixed terminal, e.g. a base station, eNodeB, repeater, and/or access point. Such a RAN typically includes a system infrastructure which generally includes a network of various fixed terminals that are in direct radio communication with the subscriber devices. Each of the fixed terminals operating in the RAN may have one or more transceivers that may, for example, serve subscriber devices in a given region or area, known as a ‘cell’ or ‘site’, by radio frequency (RF) communication. The subscriber devices that are in direct communication with a particular fixed terminal are said to be served by the fixed terminal. In one example, all radio communications to and from each subscriber device within the RAN are made via respective serving fixed terminals. Sites of neighboring fixed terminals may be offset from one another and may be non-overlapping or partially or fully overlapping with one another.
RANs may operate according to an industry standard land mobile radio (LMR) or cellular protocol such as, for example, the Project 25 (P25) standard defined by the Association of Public Safety Communications Officials International (APCO), or other radio protocols, the TETRA standard defined by the European Telecommunication Standards Institute (ETSI), the Digital Private Mobile Radio (dPMR) standard also defined by the ETSI, the Digital Mobile Radio (DMR) standard also defined by the ETSI or the Long Term Evolution (LTE) protocol including multimedia broadcast multicast services (MBMS), among many other possibilities.
Communications in accordance with any one or more of these protocols or standards, or other protocols or standards, may take place over physical channels in accordance with one or more of a TDMA (time division multiple access), FDMA (frequency divisional multiple access), OFDMA (orthogonal frequency division multiplexing access), or CDMA (code division multiple access) protocols. Subscriber devices in RANs such as those set forth above send and receive voice streams (encoded portions of voice, audio, and/or audio/video streams) in a call in accordance with the designated protocol.
LMR systems may operate in either a conventional or trunked configuration. In either configuration, a plurality of subscriber devices are partitioned into separate groups of subscriber devices. In a conventional system, each subscriber device in a group is selected to a particular frequency for communications associated with that subscriber device's group. Thus, each group is served by one channel, and multiple groups may share the same single frequency (in which case, in some embodiments, group IDs may be present in the group data to distinguish between groups using the same shared frequency).
In contrast, a trunked radio system and its subscriber devices use a pool of traffic channels for virtually an unlimited number of groups of subscriber devices (e.g., talkgroups). Thus, all groups are served by all channels. The trunked radio system works to take advantage of the probability that not all groups need a traffic channel for communication at the same time. When a member of a group requests a call on a control or rest channel on which all of the subscriber devices in the system idle awaiting new call notifications, in one embodiment, a call controller assigns a separate traffic channel for the requested group call, and all group members move from the assigned control or rest channel to the assigned traffic channel for the group call. In another embodiment, when a member of a group requests a call on a control or rest channel, the call controller may convert the control or rest channel on which the subscriber devices were idling to a traffic channel for the call, and instruct all subscriber devices that are not participating in the new call to move to a newly assigned control or rest channel selected from the pool of available channels. With a given number of channels, a much greater number of groups can be accommodated in a trunked system as compared with conventional radio systems.
Individual (e.g., one to one) or group (e.g., one to many) calls may be made between wireless and/or wireline participants in accordance with the narrowband protocol or standard. Group members for group calls may be statically or dynamically defined. That is, in a first example, a user or administrator working on behalf of the user may indicate to the switching and/or radio network (perhaps at a controller device, such as a call controller, PTT server, serving gateway, radio network controller (RNC), zone controller, or mobile management entity (MME), base station controller (BSC), mobile switching center (MSC), site controller, Push-to-Talk controller, or other network device) a list of participants of a group at the time of the call or in advance of the call. The group members (e.g., subscriber devices) could be provisioned in the network by the user or an agent, and then provided some form of group identity or identifier, for example. Then, at a future time, an originating user in a group may cause some signaling to be transmitted indicating that he or she wishes to establish a communication session (e.g., group call) with each of the pre-designated participants in the defined group. In another example, subscriber devices may dynamically affiliate with a group (and also disassociate with the group) perhaps based on user input, and the switching and/or radio network may track group membership and route new group calls according to the current group membership.
One problem that has arisen for group calls is that a target SD of the group call may enter an ongoing group call late, missing one or more portions of a voice stream in a voice call previously transmitted over a radio link due to any number of factors, including but not limited to: the target SD coming back into range after being out of range, the removal of a prior interferer within the range of the target SD or the base station serving the target SD, the avoidance of a prior geographic feature such as a building, hill, or tunnel that temporarily blocked communications between the target SD and its serving base station, the target SD powering up at or after a time the call started, or other user action at the target SD such as the swapping out of batteries. Conventionally, the user of the late entry target SD may listen to the remainder of the voice call and, during call hang time, key up and ask the source SD user to repeat what was missed. In other situations, the user of the late entry target SD may attempt to make sense and/or interpret the content or intent of the voice call using only the received portions of the voice stream.
Situations may arise, however, where the missed portions of the voice stream of the voice call are critical communications that may lead to undesired consequences if not accurately and fully rendered at all receiving SDs. For example, a situation may arise where a dispatcher or incident scene commander transmits a voice instruction instructing first responders “not to enter the building and seek survivors,” perhaps due to known structural issues with the building's roof. If, due to one of the situations noted above, a target SD of the communication receives everything in the voice stream after the word “not,” the entire context of the voice call changes and undesired consequences may result.
Accordingly, what is needed is an improved method and apparatus for replaying a missed voice stream portion at one or more late entry SDs in a voice call.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.